Retaining ring of a wafer carrier

ABSTRACT

A retaining ring of a wafer carrier includes a polymer containing abrasives. The abrasives can be released from the polymer by the friction between the polymer and the polishing pad. Therefore, it is convenient to maintain the wafer and is possible to prevent abrasives from aggregating in the polishing slurry. Meanwhile, the time for replacing the polishing slurry can be reduced and the polishing operation as a whole can be simplified so as to reduce the cost and promote productive efficiency.

BACKGROUND OF THE INVENTION

[0001] A. Field of the Invention

[0002] The invention relates to a retaining ring of a wafer carrier, andespecially to a retaining ring of a wafer carrier applicable to achemical-mechanical polishing (CMP) apparatus.

[0003] B. Description of the Related Art

[0004] With reference to FIG. 1, a conventional CMP apparatusessentially includes a polishing platen 1 for performing the waferpolishing, a polishing pad 2 mounted on the polishing platen 1, a wafercarrier 3 for maintaining a wafer 5 to be polished and a polishingslurry supply mechanism 4 for supplying polishing slurry 6.

[0005] The wafer carrier 3 essentially includes a polish head 31 and aspindle 32. As shown in FIG. 2, the polish head 31 includes a polishhead body 311, a membrane 312 and a retaining ring 313.

[0006] As shown in FIG. 3, most of the conventional retaining rings 313are made of Teflon. Because the retaining ring 313 made of Teflon willhave a relatively higher hardness, it is necessary to slightly extendthe surface of the wafer 5 out of the retaining ring 313 to prevent theretaining ring 313 from damaging the polishing pad 2 when used. It isvery inconvenient to retain the wafer 5, since the wafer 5 surface hasto be slightly exposed from the retaining ring 313 when used.Especially, the retaining ring 313 will be somewhat deformed after beingused a period of time and it is more difficult to retain a wafer 5 in adeformed retaining ring 313.

[0007] In order to resolve the above-mentioned problem, a retaining ring313 made of polyphenylene-sulfide (hereinafter also referred to PPS) hasrecently been developed by manufacturers. A retaining ring 313 made ofPPS has a relatively lower hardness. It is not necessary to particularlytake care of the relative position between the wafer 5 and the retainingring 313 when a retaining ring 313 made of PPS is used, since the partof the retaining ring 313 which extends out of the surface of the wafer5 will be abraded by friction. Therefore, it is more convenient toemploy the PPS retaining ring 313 to maintain the wafer 5.

[0008] Though the PPS retaining ring 313 is convenient in maintainingthe wafer 5, however, it does not simplify the total polishingoperation. Therefore, to maintain the convenience of retaining the waferwhile simplifying the total polishing operation is another importantproblem needed to be resolved. Here, the polishing operation alsoincludes a retaining ring replacing procedure and a polishing slurryreplacing procedure.

[0009] Though the ingredients of the polishing slurry 6 can be varieddepending on the ingredients of the wafer surface, its essentialingredients include abrasives, de-ionized (DI) water, a chemical solventor an oxidizing agent. All the conventional polishing slurries 6 includeabrasives and the abrasives inclined to aggregate into larger abrasiveswhen the polishing slurry flows in the pipe (not shown) of the polishingslurry supply mechanism after a long period of time. The largerabrasives will scratch the wafer 6 during polishing. Therefore, toprevent the wafer from being scratched by the aggregated abrasives isanother important problem to be resolved.

SUMMARY OF THE INVENTION

[0010] In view of the above, an objective of the invention is to providea retaining ring for a wafer carrier, which can conveniently retain awafer and prevent abrasive aggregation in the polishing slurry.

[0011] Another objective of the invention is to provide a retaining ringof a wafer carrier, which can reduce the time in replacing the polishingslurry and simplify the polishing operation as a whole so as to reducethe cost and to promote productive efficiency.

[0012] To achieve the above-mentioned objectives, the invention providesa retaining ring for a wafer carrier wherein the retaining ring includesa polymer containing abrasives.

[0013] With the retaining ring according to the invention, the abrasivescontained in the retaining ring will be released by the friction betweenthe retaining ring and the polishing pad. Therefore, it is not necessaryto add any abrasive in the polishing slurry and there is no problem ofabrasive aggregation in the pipe of the polishing slurry supplymechanism.

[0014] In addition, unlike prior art, it is possible to directly replacethe retaining ring without replacing the polishing slurry or cleaningthe pipe of the polishing slurry supply mechanism if one simply wants toreplace the abrasives. Even though it is necessary to replace thepolishing slurry and to clean the pipe of the polishing slurry supplymechanism, the time needed for replacing or cleaning will be shorter,since no abrasive aggregation occurs in the polishing slurry supplymechanism. Therefore, the time for replacing the polishing slurry isgreatly reduced and the polishing operation as a whole can be simplifiedso as to reduce the cost and promote productive efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] These and other objectives and advantages of the invention willbecome apparent by reference to the following description andaccompanying drawings wherein:

[0016]FIG. 1 is a schematic view showing a part of a conventional CMPapparatus;

[0017]FIG. 2 is an exploded view showing the essential part of a wafercarrier of a conventional CMP apparatus;

[0018]FIG. 3 is a partial sectional view showing a conventional wafercarrier;

[0019]FIG. 4A is a sectional view showing a wafer carrier according toone embodiment of the invention; and

[0020]FIG. 4B is a bottom view of the wafer carrier shown in FIG. 4A.

DETAIL DESCRIPTION OF THE INVENTION

[0021] In the following, a preferred embodiment according to theinvention will be described in detail with reference to FIGS. 4A and 4B.Before describing it, it is intended to point out that the samereferential numerals shown in FIGS. 1, 2 and 3 are also adopted hereinto indicate the similar elements for the sake of convenience indescribing similar elements.

[0022] With reference to FIGS. 4A and 4B, the retaining ring 313′ of awafer carrier 3 in accordance with the invention is applied to maintaina wafer 5 on a wafer carrier 3. The retaining ring 313′ is formed of apolymer containing abrasives therein. In this embodiment, suitableabrasives for forming the retaining ring 313′ include SiO₂, Al₂O₃ andCeO₂.

[0023] With the retaining ring 313′ according to the invention, theabrasives contained in the retaining ring 313′ will be released by thefriction between the retaining ring 313′ and the polishing pad 2.Therefore, it is not necessary to add any abrasive in the polishingslurry and there is no problem of abrasive aggregation in the pipe ofthe polishing slurry supply mechanism 4.

[0024] In addition, unlike prior art, it is possible to directly replacethe retaining ring 313′ without replacing the polishing slurry orcleaning the pipe of the polishing slurry supply mechanism 4, if onesimply wants to replace the abrasives. Even though it is necessary toreplace the polishing slurry and to clean the pipe of the polishingslurry supply mechanism 4, the time needed for replacing or cleaningwill be shorter, since no abrasive aggregation occurs in the polishingslurry supply mechanism 4. Therefore, the time for replacing thepolishing slurry is greatly reduced and the polishing operation as awhole can be simplified so as to reduce the cost and promote productiveefficiency.

[0025] While this invention has been described with reference to anillustrative embodiment, this description is not intended to beconstrued in a limiting sense. Various modifications and combinations ofthe illustrative embodiment, as well as other embodiments of theinvention, will be apparent to persons skilled in the art upon referenceto the description. It is therefore intended that the appended claimsencompass any such modifications or embodiments.

What is claimed is:
 1. A retaining ring of a wafer carrier applicable tomaintain a wafer on a wafer carrier, said retaining ring including apolymer and characterized by said polymer containing abrasives therein.2. The retaining ring of a wafer carrier as claimed in claim 1, whereinthe abrasive is SiO₂.
 3. The retaining ring of a wafer carrier asclaimed in claim 1, wherein the abrasive is Al₂O₃.
 4. The retaining ringof a wafer carrier as claimed in claim 1, wherein the abrasive is CeO₂.